She later told her children that Mason had become obsessive and she wanted to end the friendship.

The 68-year-old was arrested after he told police officers at Birmingham Markets that he had killed his “girlfriend”.

Birmingham Community Safety Partnership last month published a report which concluded that more could have been done by professional agencies to help Mrs Rennie.

A domestic homicide review – designed to learn lessons from household-based violence, abuse or neglect – said Mason had “long-standing mental health issues”.

But it said officials “lacked curiosity” about Mrs Rennie’s identity and the risks she was exposed to.

The review said: “There was a failure by the police to enquire about the identity of the ‘girlfriend’ and by the GP to seek further information in relation to personal problems mentioned by the victim.

“The perpetrator showed a resistance to engage with mental health services and, indeed, a decision to discharge him from the mental health service was influenced by his reluctance to engage.

“Had professional curiosity been exercised it is possible the nature of the relationship between the victim and the perpetrator would have been ascertained, which may have resulted in interventions by agencies.

“However with this lack of awareness, it is concluded that in this case the death of the victim could not have been predicted or prevented.”

“A number of recommendations identified by those agencies involved in the review have been implemented.

“Training for GPs in recognising and responding to domestic abuse has commenced.

“West Midlands Police have created adult safeguarding teams to complement and support adult abuse investigations.

“Birmingham and Solihull Mental Health Foundation Trust has also reviewed and strengthened its policy and procedure to ensure multi-agency discussions are undertaken when service users do not attend their appointments.”